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PM: runtime: Avoid device usage count underflows
A PM-runtime device usage count underflow is potentially critical, because it may cause a device to be suspended when it is expected to be operational. It is also a programming problem that would be good to catch and warn about. For this reason, (1) make rpm_check_suspend_allowed() return an error when the device usage count is negative to prevent devices from being suspended in that case, (2) introduce rpm_drop_usage_count() that will detect device usage count underflows, warn about them and fix them up, and (3) use it to drop the usage count in a few places instead of atomic_dec_and_test(). Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
parent
bd8284e968
commit
82586a7215
1 changed files with 37 additions and 7 deletions
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@ -263,7 +263,7 @@ static int rpm_check_suspend_allowed(struct device *dev)
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retval = -EINVAL;
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else if (dev->power.disable_depth > 0)
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retval = -EACCES;
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else if (atomic_read(&dev->power.usage_count) > 0)
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else if (atomic_read(&dev->power.usage_count))
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retval = -EAGAIN;
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else if (!dev->power.ignore_children &&
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atomic_read(&dev->power.child_count))
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@ -1039,13 +1039,33 @@ int pm_schedule_suspend(struct device *dev, unsigned int delay)
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}
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EXPORT_SYMBOL_GPL(pm_schedule_suspend);
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static int rpm_drop_usage_count(struct device *dev)
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{
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int ret;
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ret = atomic_sub_return(1, &dev->power.usage_count);
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if (ret >= 0)
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return ret;
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/*
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* Because rpm_resume() does not check the usage counter, it will resume
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* the device even if the usage counter is 0 or negative, so it is
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* sufficient to increment the usage counter here to reverse the change
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* made above.
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*/
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atomic_inc(&dev->power.usage_count);
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dev_warn(dev, "Runtime PM usage count underflow!\n");
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return -EINVAL;
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}
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/**
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* __pm_runtime_idle - Entry point for runtime idle operations.
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* @dev: Device to send idle notification for.
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* @rpmflags: Flag bits.
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*
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* If the RPM_GET_PUT flag is set, decrement the device's usage count and
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* return immediately if it is larger than zero. Then carry out an idle
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* return immediately if it is larger than zero (if it becomes negative, log a
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* warning, increment it, and return an error). Then carry out an idle
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* notification, either synchronous or asynchronous.
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*
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* This routine may be called in atomic context if the RPM_ASYNC flag is set,
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@ -1057,7 +1077,10 @@ int __pm_runtime_idle(struct device *dev, int rpmflags)
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int retval;
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if (rpmflags & RPM_GET_PUT) {
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if (!atomic_dec_and_test(&dev->power.usage_count)) {
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retval = rpm_drop_usage_count(dev);
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if (retval < 0) {
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return retval;
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} else if (retval > 0) {
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trace_rpm_usage_rcuidle(dev, rpmflags);
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return 0;
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}
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@ -1079,7 +1102,8 @@ EXPORT_SYMBOL_GPL(__pm_runtime_idle);
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* @rpmflags: Flag bits.
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*
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* If the RPM_GET_PUT flag is set, decrement the device's usage count and
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* return immediately if it is larger than zero. Then carry out a suspend,
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* return immediately if it is larger than zero (if it becomes negative, log a
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* warning, increment it, and return an error). Then carry out a suspend,
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* either synchronous or asynchronous.
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*
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* This routine may be called in atomic context if the RPM_ASYNC flag is set,
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@ -1091,7 +1115,10 @@ int __pm_runtime_suspend(struct device *dev, int rpmflags)
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int retval;
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if (rpmflags & RPM_GET_PUT) {
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if (!atomic_dec_and_test(&dev->power.usage_count)) {
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retval = rpm_drop_usage_count(dev);
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if (retval < 0) {
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return retval;
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} else if (retval > 0) {
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trace_rpm_usage_rcuidle(dev, rpmflags);
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return 0;
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}
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@ -1527,14 +1554,17 @@ EXPORT_SYMBOL_GPL(pm_runtime_forbid);
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*/
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void pm_runtime_allow(struct device *dev)
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{
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int ret;
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spin_lock_irq(&dev->power.lock);
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if (dev->power.runtime_auto)
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goto out;
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dev->power.runtime_auto = true;
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if (atomic_dec_and_test(&dev->power.usage_count))
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ret = rpm_drop_usage_count(dev);
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if (ret == 0)
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rpm_idle(dev, RPM_AUTO | RPM_ASYNC);
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else
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else if (ret > 0)
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trace_rpm_usage_rcuidle(dev, RPM_AUTO | RPM_ASYNC);
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out:
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